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This blog is expressly directed to readers who do not have strong training or backgrounds in science, with the intent of helping them grasp the underpinnings of this important issue. I'm going to present an ongoing series of posts that will develop various aspects of the science of global warming, its causes and possible methods for minimizing its advance and overcoming at least partially its detrimental effects.

Each post will begin with a capsule summary. It will then proceed with captioned sections to amplify and justify the statements and conclusions of the summary. I'll present images and tables where helpful to develop a point, since "a picture is worth a thousand words".

Wednesday, September 29, 2010

Today’s CO2-Emitting Devices Add to Tomorrow’s Global Warming

Note:  This posting discusses an article by Davis and coworkers.  The posting immediately following this one discusses a commentary by Hoffert on the Davis article.

Summary:  The world-wide transportation, space heating and electric generating installations currently in use will continue to produce new CO2 (greenhouse gas) emissions for decades, adding to global warming.  Imagine that as of today we abruptly cease to manufacture new cars, planes, furnaces and air conditioning, and stop commissioning new electric power plants.  Even so, existing facilities and apparatuses, given their expected service times, would add sufficient new CO2 to the atmosphere    that the global mean temperature would likely rise about another 0.6 deg C (1.1 deg F) from today’s level by 50 years from now.  In actual fact, however, addition of new fossil fuel-burning facilities will not cease, and indeed will greatly expand, making global warming even worse.  Accordingly it is imperative to transform the world’s energy economy to one that relies mainly on alternative and sustainable energy sources and on devices adapted to use them.

Introduction.  The world’s nations already have enormous numbers of cars, airplanes, power generating plants, and heating and cooling facilities installed throughout their economies.  Yet as a consequence of globalization and human aspiration, there is a desire, if not a need, to add even more such facilities and items, probably increasing their numbers by large factors in the remainder of this century.  These new additions to global CO2-producing capacity constitute a critical danger exacerbating global warming.

Atmospheric CO2 will increase in the next 50 years due to existing installations.  In the September 10, 2010 issue of Science, Davis, Caldeira and Matthews (Vol. 329, p. 1330-3; see Note 1) report an analysis in which they imagine that no new CO2-generating facilities are added in the next 50 years.  They assess the future production of atmospheric CO2 (committed CO2) and its effect on global temperature from only CO2-producing equipment already in place.  This assessment was carried out using available data for world-wide fixed sources (e.g. power plants, residences and work places) and transportation equipment. They use a commonly accepted global climate model to make their projections.

Their analysis predicts that the global concentration of atmospheric CO2 will increase from the present 390 parts per million (ppm; parts by volume of CO2 gas per million parts by  volume of air total), to a predicted maximum of about 412 ppm at about 2037.  (A sense of how much CO2 is produced by burning one tankful of gasoline can be seen here.)  After 2037 the predicted CO2 concentration falls slightly to about 408 ppm by 2060. (See Fig. 1C from Davis and coworkers below). 

Gt CO2 stands for gigatons of CO2, where 1 gigaton is 1 billion tons, and 1 ton is a metric ton, 1000 kg, or about 2200 lbs.  In Figs. 1A and 1B the number for each colored band is the total committed Gt CO2 for that band. 
© American Association for the Advancement of Science.  Presentation of this Figure  here is believed to comply with the "Fair Use" limitations (sections 107 and 108) of US Copyright law.

In greater detail, the incremental increase in CO2 concentration in the atmosphere year by year starts out high, as all the facilities and equipment are active. (See Figs. 1A (graphed according to energy sector)  and 1B (graphed according to country/region) from Davis and coworkers).   Year by year as installations reach the ends of their predicted lifetimes and are taken out of service (based on historical useful lifetimes of comparable equipment) the annual increments diminish more or less in a straight line, falling to no further increment by about 2046 (i.e., 36 years from now).  These increments are superimposed on a baseline of CO2 annual additions that remain essentially constant throughout the 50 year span arising from “non-energy” sources, which are exemplified by cement and steel manufacture, and agriculture.  For this reason the annual CO2 increments never fall to zero. 

Global temperature is predicted to rise from its present level in the next 50 years.  Davis and coworkers depict the current average global temperature as being about 0.7 deg C (1.3 deg F) higher than it was in preindustrial times.  They predict that as a result of the increased atmospheric CO2 concentration arising from existing installations (Fig. 1C above) the average global temperature rises slowly over the next 50 years, reaching 1.3 deg C (2.3 deg F) above average preindustrial temperature by 2060. (See Fig. 1D above). 

Further detail: Predicted upper and lower bounds.  In Fig. 1, predicted upper and lower bounds to the changes shown are given by the dashed lines in Figs. 1A and 1B, and by the red and blue lines, respectively, in Figs. 1C and 1D.  These are based on higher and lower assumed production levels for CO2 than used in the median analysis.

Significance for global warming.  Davis and coworkers show that existing CO2-producing installations and devices lead to seemingly modest further increases in atmospheric CO2 levels and predicted further global temperature increases.  There is no comfort in these findings, however (see the next blog posting describing the article by Hoffert).  First, these predictions are due only to existing facilities.  There is no doubt that many more power generating plants, automobiles, and home heating and cooling capabilities that produce CO2 will be built over the 50 years covered.  This is because many areas of the world are only now passing from “undeveloped” to “developing” status, and currently developing countries are adding to demand for these devices and installations as well.  Second, as Davis and coworkers point out, other activities that lead to more burning of fossil fuels were not analyzed, but are significant.  These include transportation fuel distribution infrastructure, and highway development.

Conclusion. Davis and coworkers conclude “satisfying growing demand for energy without producing CO2 emissions will require truly extraordinary development and deployment of carbon-free sources of energy, perhaps 30 TW [terawatts, or trillion watts] by 2050 [citations omitted]. Yet avoiding key impacts of climate change depends on the success of efforts to overcome infrastructural inertia and commission a new generation of devices that can provide energy and transport services without releasing CO2 to the atmosphere.”

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Note 1. Available online for a fee or through personal or institutional subscription.  Many public libraries, and university libraries open to the public, receive the journal.

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